I think the new move commit system is really cool. Have you ever had a decent move set up, and you wanted to see if you could improve it, but you were afraid to start changing things around because you didn't want to run out of time with a bad move selected? Move Commit can help! Here's how it works:
When you have a good move set up, and time left on the clock, press Q. Now that move is your "committed move". Feel free to move your joints around and try for something better. If you get something worse, don't worry: when the timer runs out, your committed move is automatically restored and that's the one you will perform. But if you get something you like better, just press Q again and now that one is the committed move.
You can also manually go back to the committed move by pressing Shift-Q.